I'm trying to make a set of scale retracts out of aluminium tube (7/32",
3/16" and 5/32") but wondering how best to join the parts. I know that if I
want to WELD aluminium then I need to TIG weld it, but is it possible to
braze/silver solder this?
I should know the answers, coming form an engineering background, but it's
been a while...
On 5/25/2004 3:10 PM Ted shuffled out of his cave and grunted these
great (and sometimes not so great) words of knowledge:
They have specialty rods available for "welding" aluminum. It is
actually brazing and done with a propane torch. I have used them in the
past on an aluminum storm window frame with excellent results. Your
local hardware store should be able to get them for you. If I remember
correctly, a pack of 5 rods runs about $10.
Its p[ossible to soft solder it useing aluminium specificflux and a
special solder, although for electrical ork, standard multicire seems to
However I would regard epoxy as a stringer solution.
I have welded aluminium years ago as an apprentice, usng oxy acetylne.
Bloody mess. Very hard to stop it meliting.
If these are to be butt joined, then you will never be able to trust their
strength. The brazing rods sometimes work great and other times fail
completely. If you are going to slide one inside the other, there are very
good structural epoxies for that.
What I've actually got is a sort of T-piece, with one length of tube passing
at right angles through a hole drilled in the other. After looking a bit
deeper on the web, it would appear that I can use silver solder on
aluminium, so maybe I'll give that a go.
Thanks for the tips,
Well even tho I have been soldering for 40 years (professionally as a TV tech
and also as a hobbyist) I have never been able to solder aluminium using
standard multicore - in the days when I used aluminium chassis to build radios
and amps always had to use a solder lug for the earth connection.
What is your secret?
The Natural Philos>
Best results I've had are with a kit of alum rods, stainless wire brush, a
10 inch length of stainless wire about 1/16" diameter and very clear
instructions. No flux ! This was marketed by an outfit calling themselves
Techno-Weld in UK. The length of wire is referred to as an "abrading tool"
! It worked well every time. Starting with some sample test pieces I
eventually graduated to making in-cowl mufflers and repairing broken
mufflers which were the trickiest jobs I tried. I have never tried brazing
anything required to take heavy, shock loads like a landing gear strut.
The trick was always to keep brushing the areas to be joined clean and
bright with the brush and difficult corners with the wire abrader. You will
need a gas torch of the right size. Small is better - but if too small, the
parts won't take - if too large, the parts may melt - especially if the
material is thin walled. For in-cowl mufflers, I found it helped to make a
"nest" of four bricks around the components - this seemed to help by keeping
the heat confined more evenly around the parts - two bricks side by side and
two on top making an angle of 90 degrees. Be careful of burning your
fingers - I know. Hope this helps.
Not mine. I simply needed to solderalumium tabs on some LIPO cells I had
bought. A google search got me to a model train shop who sold me some
Carrs Grey Flux. That was the killer breakthrough. With a hotttest irin
setting and an open window (fumes are VERY unpleasant), I gobbed this
blue jelly onto some baking foil, fed in multicore, and by golly it
Once tinned of course the problem was solved.
I note you are in Oz. Try a google search on 'alumiium solder paste' and
Carrs are, I think UK bvased, but have European and commonwealth reach,
whereas US suppliers seem to have the paste more.
The paste is, I think, mixture of solder and flux.
Try it, but remember aluminium aircraft are bonded together with epoxy.
Given the arrangement you have, that might be the easiest solution, and
if you are painting the result, just as acceptable as brazing.
How come no-one has mentioned argon arc welding ?
When I was a young sprog (back in the mists of time) aluminium was
welded by means of argon arc and (I think - it was a while ago)
aluminium rods of different gauge.
The chap who normally did the argon welding was playing about one day
and actually welded 2 pieces of aluminium foil together.
Has argon arc gone out with the ark ???
Seems to me that it's used in some TIG welding:
"Argon is used primarily for its properties an inert gas in
applications such as arc welding, steelmaking, heat treating, and
electronics manufacturing. It is also widely used as a fill gas in
incandescent and fluorescent lamps. In its welding application,
straight argon is generally used as a shielding gas in tig welding,
while mig welding is usually best suited to a mixture of argon and CO2
as its shielding gas."
"Shielding Gases used in TIG welding:
Argon + Hydrogen
Helium is generally added to increase heat input (increase welding
speed or weld penetration). Hydrogen will result in cleaner looking
welds and also increase heat input, however, Hydrogen may promote
porosity or hydrogen cracking."
The Tungsten Inert Gas (TIG) welding method was developed in the 1940s
for welding of aluminum and magnesium alloys.
Besides aluminum and magnesium, the TIG method is used to weld
stainless steels, as well as carbon and low-alloy steels. The primary
application area for TIG is welding of thin metals, < 6 mm.
In TIG welding, an electric arc is used to heat and melt the material.
The electric arc burns between the electrode and the workpiece. A
shielding gas that flows through the gas nozzle protects the weld pool
and the electrode. The electrode is centrally positioned in the gas
The key purpose of the shielding gas in TIG welding is to protect the
hot and molten parts of the workpiece, the filler metal and the
electrode from the deleterious influence of the surrounding air. In
addition, the shielding gas affects the characteristics of the arc and
the appearance of the weld.
Typical shielding gases consist of argon, helium or mixtures thereof.
The addition of hydrogen or nitrogen can also be beneficial under
Typical applications for TIG welding are welding of pipes, pressure
vessels and heat exchangers. Since TIG welding can be used to weld
thin metals and small objects, the method is also used in the
The advantages of TIG welding include very high weld quality, absence
of slag and very little spatter. The method is extremely versatile,
since most weldable materials can be TIG-welded and many welding
positions and joint configurations can be used.
That was mentioned in the original post. Heli-arc welding is the same as
the older argon arc welding with only a change in gasses. I don't have the
money for the equipment and I doubt that most modelers do, either (judging
by how much they complain about a $5.00 increase in dues!)
"Heliarc" seems to be a registered trade name for TIG welding:
Advantage Fabricated Metals performs a number of welding processes.
The two most common welding processes we use include TIG, an acronym
for Tungsten Inert Gas welding and MIG, an acronym for Metal Inert Gas
welding. TIG is also referred to as GTAW (Gas Tungsten Arc Welding)
and Heliarc®. MIG also is referred to as GMAW (Gas Metal Arc Welding).
We also provide oxy-acetylene welding.
TIG welding is also called GTAW (Gas Tungsten Arc Welding) and
Heliarc® welding. Heliarc® was the trade name given to the process by
Linde's when it was introduced decades ago. The arc is started with a
tungsten electrode shielded by inert gas and filler rod is fed into
the weld puddle separately. The gas shielding that is required to
protect the molten metal from contamination and amperage are supplied
during the TIG welding operation.
TIG welding is a slower process than MIG, but it produces a more
precise weld and can be used at lower amperages for thinner metal and
can even be used on exotic metals. TIG welding is a commonly used high
quality welding process. TIG welding has become a popular choice of
welding processes when high quality, precision welding is required.
The TIG welding process requires more time to learn than MIG. It is
similar in technique to gas welding.
Gas tungsten arc welding (GTAW) had its beginnings from an idea by
C.L. Coffin to weld in a nonoxidizing gas atmosphere, which he
patented in 1890. The concept was further refined in the late 1920s by
H.M.Hobart, who used helium for shielding, and P.K. Devers, who used
argon. This process was ideal for welding magnesium and also for
welding stainless and aluminum. It was perfected in 1941, patented by
Meredith, and named Heliarc® welding. It was later licensed to Linde
Air Products, where the water-cooled torch was developed. The gas
tungsten arc welding process has become one of the most important.
The gas shielded metal arc welding (GMAW) process was successfully
developed at Battelle Memorial Institute in 1948 under the sponsorship
of the Air Reduction Company. This development utilized the gas
shielded arc similar to the gas tungsten arc, but replaced the
tungsten electrode with a continuously fed electrode wire. One of the
basic changes that made the process more usable was the small-diameter
electrode wires and the constant-voltage poser source. This principle
had been patented earlier by H.E. Kennedy. The initial introduction of
GMAW was for welding nonferrous metals. The high deposition rate led
users to try the process on steel. The cost of inert gas was
relatively high and the cost savings were not immediately available.
Welding aluminum is done using two preferred methods, both of which
employ inert gases, pure argon, or a mix of argon with helium. Any
contamination of these gases causes oxidation of the weld, as Uebele
inadvertently demonstrated trying to repair a mag-wheel.
?Mag-wheels are not magnesium, you know. They?re aluminum,? Uebele
said. ?I knew that, of course, but the weld kept turning black on me.
Finally, I checked the gas supply and discovered I was using an
argon-carbon dioxide mix. We use carbon dioxide for welding carbon
steel. To weld aluminum you?ve got to use pure argon. We don?t use
helium here. It?s too expensive. But they do mix argon and helium to
increase welding temperatures for thicker sections.? Argon is about
ten times the cost of carbon dioxide, commonly used to weld carbon
steel. Helium costs another $12 per cubic feet than argon.
During WW II, TIG welding was developed. Old timers also called this
process heliarc welding. The word heliarc was a trademark of Linde Air
Products. Like many known trade marks the name became generic for TIG
welding. The Linde Air name was sold to the German subsidiary for $60
million, and Linde became known as Praxair in the U.S.
Today, TIG and MIG welding are the two recommended options for welding
aluminum. TIG means tungsten-inert-gas, a shorter acronym for
gas-tungsten-arc-welding (GTAW). The process uses a hand torch with a
non-consumable tungsten or tungsten alloy electrode to strike an arc.
Pure argon and/or helium, both non-flammable inert gases, provide the
shield around the weld to prevent weld contamination from oxides and
hydrogen absorption. A filler rod of aluminum is fed into the molten
weld, wherever filler is necessary.
Thanks for the informative posts Martin.
I remember the argon-arc process from a shipyard back in the early
1960's. There was a welding set (similar to ordinary arc-welder) with
the addition of a large argon bottle. The argon was fed by a pipe to the
welding tool... this resembled a gun type nozzle. The arc would be
started and the gas would surround the area to be welded. Hand held
aluninium rods (like in oxy-acetylene welding) were used to feed extra
metal into the weld..... it was a long time ago but I remember the setup
produced very nice welds and was reputed to be a very bad system to
suffer a "flash" from. One guy ended up in hospital his eyes were so badly
I would have thought a small aluminium welding job could be done fairly
cheap by most small engineering firms and would be better than messing
about with alternatives.
You're most welcome. It's a topic that interests me.
I'm not a welder; I just play one in my dreams. :o)
That never happens to me in my dreams. All my
welds are perfect!
I'm tempted to try my hand at pop rivets & JB Weld. I'd love
to be able to cook up totally customized mufflers for myself.